How to Create a Global Class?

Question

I have a class that i want to make a global class. The Global class have variables that i want to initialize in Main Activity class. Then I want to get the value of variables from Global class and set it to show in Textview of Second Activity Class. I have coded it to but i am getting an error. don't know what is wrong with it. I will be thankful to the person who will try to give the solution to it.

This is the GlobalClass.java

import android.util.Log;

public class GlobalClass {
 private String name;
 private String email;


 public String getName() {
    return name;
 }
 public void setName(String name) {
    this.name = name;
 }
 public String getEmail() {
    return email;
 }
public void setEmail(String email) {
    this.email = email;
}

}

This is the MainActivity.java Class. In this Class i want to initialize the variables of GlobalClass.java. However I am getting error int this line "final GlobalClass test=(GlobalClass)getApplicationContext();" and the error says "Can not cast from Context to GlobalClass"

public class MainActivity extends Activity {
Button btn;
Context context;

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    btn = (Button) findViewById(R.id.button1);      




    final GlobalClass test=(GlobalClass)getApplicationContext();// 

    globalVariable.setName("THis is me");
    globalVariable.setEmail("sbd@somewhere");

    btn.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub

    Intent intent = new Intent(getBaseContext(),SecondScreen.class);
            startActivity(intent);
        }
    });
}
}

This is my SecondScreen.java Class. I want to Get the values of variables in GLobalClass.java in this class.

public class SecondScreen extends Activity {
 TextView tv;
 Button btnButton;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_second_screen);
    tv= (TextView) findViewById(R.id.tv);
    btnButton=(Button) findViewById(R.id.thirdBtn);


    final GlobalClass globalVariable=(GlobalClass)getApplicationContext();
    final String name= globalVariable.getName();
    final String email= globalVariable.getEmail();

    String print= "Name: "+name+" Email:"+email;
    tv.setText(print);

    btnButton.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub
        Intent intent= new Intent(getBaseContext(),ThirdScreen.class);
            startActivity(intent);

        }
    });
}

}

This is my Manifest Class

?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.arifhaq.testexample"
android:versionCode="1"
android:versionName="1.0" >


<uses-sdk
    android:minSdkVersion="8"
    android:targetSdkVersion="17" />

<application
    android:name="com.arifhaq.testexample.GlobalClass"
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name="com.arifhaq.testexample.MainActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity
        android:name="com.arifhaq.testexample.SecondScreen"
        android:label="@string/title_activity_second_screen" >
    </activity>
    <activity
        android:name="com.arifhaq.testexample.ThirdScreen"
        android:label="@string/title_activity_third_screen" >
    </activity>
   </application>

 </manifest>

check this http://developer.android.com/reference/android/app/Application.html — Raghunandan, Mar 25 '14 at 13:48
I guess i have tried that and still getting the same error message. — user3393926, Mar 25 '14 at 13:55
The error says "Can not cast from Context to GlobalClass" in Main Activity class and i also pointed it out in the description part of the post above. Thanks all for your early replies. — user3393926, Mar 25 '14 at 13:58

score 1 · Accepted Answer · answered Mar 25 '14 at 14:00

1

Global class needs to extends application. You could do something like the following.

public class GlobalClass extends Application {
    public static GlobalClass instance;
    public void onCreate() {
        instance = getApplication();
    }
}

answered Mar 25 '14 at 14:00

graviton

465
3
13

score 0 · Answer 2 · answered Mar 25 '14 at 13:52

0

Usually you initialize your variables and stuff on Start of your Application to make sure u dont use uninitialized variables. You can do that in androit with onCreate() http://developer.android.com/reference/android/app/Application.html#onCreate()

answered Mar 25 '14 at 13:52

malle

334
4
17

score 0 · Answer 3 · edited May 23 '17 at 11:57

0

You should let your global class extend Application.

An extensive answer can be found here:
How to declare global variables in Android?

edited May 23 '17 at 11:57

Community

1
1

answered Mar 25 '14 at 13:53

Kaschwenk

522
5
16

How to Create a Global Class?

3 Answers3